STM32L162VC datasheet(71/123 Pages) STMICROELECTRONICS

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STM32L162VC, STM32L162RC

104

Note:

For CL1 and CL2, it is recommended to use high-quality ceramic capacitors in the 5 pF to

15 pF range selected to match the requirements of the crystal or resonator (see Figure 15).

CL1 and CL2, are usually the same size. The crystal manufacturer typically specifies a load

capacitance which is the series combination of CL1 and CL2.

Load capacitance CL has the following formula: CL = CL1 x CL2 / (CL1 + CL2) + Cstray where

Cstray is the pin capacitance and board or trace PCB-related capacitance. Typically, it is

between 2 pF and 7 pF.

Caution:

To avoid exceeding the maximum value of CL1 and CL2 (15 pF) it is strongly recommended

to use a resonator with a load capacitance CL ≤7 pF. Never use a resonator with a load

capacitance of 12.5 pF.

Example: if the user chooses a resonator with a load capacitance of CL = 6 pF and Cstray =

2 pF, then CL1 = CL2 = 8 pF.

Figure 15. Typical application with a 32.768 kHz crystal

tSU(LSE) is the startup time measured from the moment it is enabled (by software) to a stabilized

32.768 kHz oscillation is reached. This value is measured for a standard crystal resonator and it can vary

significantly with the crystal manufacturer.

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